I've rooted my Note 3, froze the Samsung Music app, and now control Google Music via the Media Controller app on the gear. Everything is working perfectly.
So is it possible to prevent the Tizen update? I'm assuming I would need to freeze something on my Note 3 in Titanium Backup.
(I also have lots of side loaded Android apps that I don't want to lose, so I really want to just freeze the Gear as-is - I'm very, very happy with exactly the way it is right now.)